It seems to me that an API and a family of open-source implementations (in Python, Ruby, PHP, Java, .NET on the server side and HTML5 on the client) supporting all of this, with accessibility and multi-lingual support designed in from the beginning, would be a great project for the innovation challenge to support. And there are a couple things I’d add to it as well:

support for various business models including subscription, advertising, sponsorship, app sales, etc.. A great discussion area should be a profit center for a news organization, and participating actively in comments should be a way for small businesses to help promote their products and for participants to help their careers

Revisiting the project’s review criteria: If implemented, especially with the up-front consideration of business model and early involvement by the project’s outtandnding media partners, involved in the project, it’s likely to get broadly adopted. It’s a unique solution: no other open-source project is looking at anything on this scale. Mojo’s resources (an online learning class for 60 people, a 15-person hackathon in Berlin, and 15 fellowships) are enough to make a significant impact if they can catalyze an open source projects.